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Moon and Companions

November 17, 2011

The last-quarter Moon, a bright star, and an even brighter planet team up to put on a good show late tonight. They’re all in view by around 1 a.m., and stand high in the south at first light.

The star is Regulus, which is to the lower left of the Moon as they rise. It’s the brightest star of Leo, and represents the lion’s heart.

Regulus is fairly close as stars go — 79 light-years. That means the light we see from Regulus tonight actually left the star’s surface 79 years ago, during the depths of the Great Depression. Light travels almost six trillion miles every year, which means that the distance to Regulus is close to half a quadrillion miles — a five followed by 14 zeroes.

Look just to the lower left of Regulus for the planet — orange Mars. It’s more than half-again as bright as Regulus is, so it stands out. And it’ll get even brighter through the end of the year and into next year.

Mars is getting brighter because it’s getting closer. Right now, it’s about 135 million miles away. At that range, light takes about 12 minutes to travel between Mars and Earth. But Earth follows a smaller, faster orbit around the Sun, so we’re catching up to our bright neighbor. When we pass it in March, the planet will be just half as far away as it is now.

If you miss Mars, Regulus, and the Moon tomorrow, try again on Saturday, when the Moon will be a little below its companions. More about that tomorrow.


Script by Damond Benningfield, Copyright 2011


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